Change menu_headings to accept color and attribute

Instead of just accepting an attribute, it's now possible to
use a color, or both color and attribute, for example:

OPTIONS=menu_headings:inverse
OPTIONS=menu_headings:red
OPTIONS=menu_headings:red&underline

Default is still just inverse.
This lets the player change the menu heading color without
needing to use menu colors for them.

Also makes it so the core uses NO_COLOR instead of 0, for all
the menu lines which don't have any prefedefined color.

Tested for tty, curses, x11, qt, and win32

doc/window.txt

@@ -381,20 +381,7 @@ add_menu(windid window, glyphinfo, const anything identifier, char accelerator,
 		   If a window-port does not support all of these, it may map
 		   unsupported attributes to a supported one (e.g. map them
 		   all to ATR_INVERSE).
-                -- clr color will hold a color value including 24-bit
-                   true color values. To do that, and make it
-                   distinguishable on the windowport side of things, the
-                   windowport needs to treat it as follows:
-                      0      = not used, just ignore the clr value.
-                      1-16   = indicates a normal NetHack color value from
-                               0 - 15, so subtract 1 to get the NetHack
-                               color value.
-                      17...  = indicates a 24-bit RGB color value, so
-                               subtract 17 to get the actual 24-bit
-                               color value.
-                   When placing the values into this parameter, the core
-                   will add 1 to a NetHack color value, and add 17 to a
-                   24-bit RGB color value. 
+                -- clr is color and is one of the NetHack CLR_ defines.
                 -- str is a pointer to the menu item text.
 		-- itemflags on this item (such as MENU_ITEMFLAGS_SELECTED etc.).